1. Field of the Invention
The invention relates to a drive apparatus for a motor vehicle, having a hollow portal axle which accommodates two electrical machines, within each case one wheel being rotatably mounted in the region of the two ends of the portal axle and it being possible for each wheel to be driven only by means of the electrical machine which is associated with said wheel, and having a step-down gear mechanism which is arranged between the respective electrical machine and the wheel which is associated with said electrical machine.
2. Description of the Related Art
A drive apparatus of this kind, which is used in a utility vehicle, is known from DE 295 18 401 U1. This utility vehicle is a city bus for transporting people. In city buses, a carriage floor which is arranged at a low level and runs through the entire bus is required, in particular in the region of the rear axle which is in the form of a rigid axle. In order to achieve this, the hollow portal axle is provided with the two electrical machines which are accommodated by said portal axle and which are in the form of electric drive motors. A step-down gear mechanism, which is in the form of a spur gear stage, is arranged between the respective electrical machine and the wheel which is associated with said electrical machine.
A drive apparatus having the features of the type mentioned in the introduction is also known from DE 296 11 867 U1.
DE 44 34 237 A1 discloses a vehicle axle having two electrical single-wheel drives, in particular for agricultural vehicles. The two single-wheel drives can be connected in a force-fitting manner by means of a clutch in order to avoid overloading of one single-wheel drive over a relatively long period of time in the event of non-uniform loading of the drive wheels of the vehicle axle. The respective electric single-wheel drive is connected to a step-down gear mechanism, which is in the form of a spur gear stage, and said step-down gear mechanism is connected to a planetary gear mechanism which is connected to the wheel which is associated with this single-wheel drive. The axle of the wheel is arranged radially offset in relation to the rotation axis of the rotor of the electric motor. The electrical input energy for the respective electric motor is generated, in particular, by a generator which is driven by the vehicle's own internal combustion engine.
DE 10 2004 003 634 A1 discloses a portal axle drive of a motor vehicle, with the flow of torque in relation to the respective wheel being introduced from a planetary gear mechanism into the output shaft, which is connected to the wheel in a rotationally fixed manner, via a step-down gear mechanism which is in the form of a spur gear stage.
DE 202 13 670 U1 describes a directly driven drive axle of a motor vehicle having two electric drive motors which are mounted in a common housing.
One disadvantage of the described drive apparatuses or axle designs is, in particular if these designs relate to a portal axle, that they are in the form of rigid axles. For vibration and comfort reasons, drive apparatuses of this kind are therefore reserved for use in utility vehicles, for example in buses or agricultural vehicles.
The object of the present invention is to provide, in a drive apparatus of the kind mentioned in the introduction, a separate connection from the respective wheel to the step-down gear mechanism, said connection permitting the wheel to be mounted in a non-rigid manner.